Keyboard switch assembly

ABSTRACT

A keyboard switch assembly comprising a flat board printed with key input circuits and perforated with a plurality of apertures; and a plurality of key switch units inserted into the apertures, the unit consisting of a key guide member of synthetic resinous material, a key longitudinally slidable therethrough and a magnetic reed switch connected to the key input circuit so as to be actuated upon key depression.

United States Patent Iwashima et a]. [45] July 18, 1972 [54] KEYBOARD SWITCH ASSEMBLY [72] Inventors: Hldeo lwashima; Satoshi Fukao, both of [56] Rem-mm cued Alchi-ken, Japan UNITED STATES PATENTS Assignee= Brother ay Kabushiki Kaisha, y 3,260,819 7/1966 Scuitto et a] ..33s/207 x Shl, Japan 3,486,145 12/1969 Paige ..335/206 [22] Fned: May 1971 Primary Exarnineh-Roy N. Envall,.1r. v [21] Appl. No.: 143,092 Attorney-Flynn & Frishauf [30] Foreign Application Priority Data [57] ABS CT A keyboard switch assembly comprising a flat board printed May 19, 1970 Japan ..45/42766 with y input circuits and perforated with a plurality of p tures; and a plurality of key switch units inserted into the aper- [52] US. Cl. ..335/206, 200/5 A, 200/159 B, tures, the unit consisting of a key guide member of Synthetic 197/98 317/ 317/112 resinous material, a key longitudinally slidable therethrough [51] Int. Cl. ..H0lh 13/00 and a magnetic reed switch connected to the key input i i [58] Field of Search ..200/5 A, 5 R, 1 A; 335/205, so as to be actuated upon key depression 335/206, 207; 340/365 R; 197/98; 317/101 C, 101 CC, IOICP, 112,113

9 Clairm, 14 Drawing figures SHEET 1 [1F 4 FIG.

PATENTED JUL! 8 m2 3, 7 3424 sum 3 nr 4 FIG 6 F I G. 7

PATENTED JUL! 81972 SHEET U [1F 4 FIG. 12

FBG.

KEYBOARD SWITCH ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to a keyboard switch assembly for use with calculators including the electronic type.

With a prior art calculator, the frame on which there is mounted a key mechanism consists of an upper plate constituting a keyboard and an opposite lower plate forming a base plate to which there are fitted reed switches, said plates acting to guide the keys. However, such arrangement is uneconomical in that the frame has to be formed of two plates. Further there has been proposed a frame constructed by forming key guide portions when the frame is molded and then mounting keys and reed switches thereon, so as to guide the keys only by the key guide portions. With this type of frame, the electrical circuits connected to the reed switches are disposed on a base plate provided separately from the keyboard, sothat connection between the switches and circuits has to be efiected by a large number of electrical wires.

. Consequently a keyboard switch assembly using the aforesaid type of frame has been .encountered with the drawbacks that not only maintenance, inspection and repair are difficult to carry out, but also due to integral formation of the key guide portions with the keyboard it is impossible to form a key guide portion, key and reed switch into one unit and use the resulting key board assembly in other types of calculators, for example, an electronic type.

SUMMARY OF THE INVENTION It is accordingly an object of this invention to provide a compact, mechanically as well as electrically stable keyboard switch assembly wherein unitization is realized by causing a single flat board concurrently to act as a printed circuit board and a keyboard.

Another object of the invention is to provide a keyboard switch assembly which minimizes wiring work and prominently facilitates assembly, maintenance, inspection and repair by forming a printed circuit and keyboard into an integral unit.

Still another object of the invention is to provide a keyboard switchassembly which can be used as it is with various types of calculator due to unitization ofthe main part.

According to this invention, there is provided a keyboard switch assembly comprising a printed circuit board perforated with a plurality of apertures; and a plurality of key switch units, each consisting of a key guide member of synthetic resin inserted into the aperture so as to be fixed to the printed circuit board, a key longitudinally slidable through the key guide member and a magnetic switch for closing a key input circuit included in the printed circuit board upon key depression.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a keyboard switch assembly according to an embodiment ofthis invention;

FIG. 2 is a bottom view of the assembly shown in FIG. 1;

FIG. 3 is a plan view of a printed circuit board of the keyboard switch assembly;

FIG. 4 is an exploded perspective view of part of the printed circuit board and a key guide member inserted into the board;

FIGS. 5 and 6 are respectively a plan view and a bottom view of the key guide member as shown in FIG. 4;

FIG. 7 is a front sectional view along line VIIVII of FIG. 5;

FIG. 8 is a vertical section along line VIIIVIII of FIG. 5;

FIG. 9 is a right side view of FIG. 7;

FIG. 10 is a rear view illustrating how to fix the key guide member into a keyboard;

FIG. 11 is a side sectional view of an assembled key switch unit of the keyboard switch assembly;

FIG. 12 is a vertical section along line XIIXII of FIG. 10; and

FIGS. 13 and 14 are respectively a plan view and a bottom view of-the key switch unit.

2 DETAILED DESCRIPTION OF THE INVENTION Throughout the figures, numeral 11 denotes a printed circuit board or keyboard of synthetic resin (or a flat board), the plain surface of which is perforated with eighteen apertures 14 into which to fit digit keys and function keys 12. From one side of said surface outwardly extends a plug 15 having a plurality of plug contacts 16 arranged in parallel. On the upper surface of the printed circuit board 11 are printed external circuits or key input circuits 17 made of conducting material. One end of the circuit 17 is connected to the corresponding plug contact 16. At the other end or intermediate part of said circuit is formed a small hole or holes 18 so as to allow the lead wires of the later described magnetic reed switches to be connected to the printed circuit board 11 from its underside. In FIG. 3, to avoid complication of the presentation, there is omitted the joint between the key input circuits l7 and plug contacts 16.

Referring to FIG. 4, numeral 19 represents a key guide member. This guide member 19 comprises a rectangular parallelepiped or a key holding pendent body 20 having a recess 21 formed at the front; switch holding portions or guide plates 22 and 23 extending forward in parallel with each other from both sides of said parallelepiped 20; and flange portions 24 horizontally extending lengthwise as well as crosswise from the top of the parallelepiped 20 and, as viewed from above it, approximately forming an I'I-shape. The aforesaid recess 21 has a substantially U-shaped cross section and, is open at the bottom. Between the top of the recess 21 and that of the para]- lelepiped 20 is formed a shoulder 25 having a thickness equal to or larger than a sum of the thickness of the flange portions 24 and that of the printed circuit board. The parallelepiped 20 is perforated with a hole elongated in the lengthwise direction of said parallelepiped 20 and penetrating it from the top of the key guide member 19 to that of the recess 21 so as to allow the key 12 to be inserted therethrough. Further, there are formed a pair of grooves 27 for guiding the key 12 which extend from both upper ends of the elongated hole 27 to both bottom ends of the recess 21. The lower end of the guide plate 22 is at a higher level than the bottom plane of the parallelepiped 20. At said lower end of the guide plate 22 is provided a notch or receptacle 28 having a sufficient width and length to cause the lead wire of the later described magnetic switch to be inserted therethrough from the bottom of the parallelepiped 20. The guide plate 23 is so formed as to extend slightly longer than the other guide plate 22 in the forward as well as downward direction of the parallelepiped 20. In the lower end of the guide plate 23 is formed a notch or receptacle 29 for firmly holding one end of the capsule of the magnetic reed switch. Further at the top of the receptacle 29 is formed another narrow upwardly extending notch 30. At the center of the inner wall of the guide plates 22 and 23 respectively is fixed a holding means 31 made of elastic material (hereinafter referred to as a holder"). Said holder 31 is in the form of a wedge shaped tab, or preferably in the form of a rectangular triangle. The holder 31 slantwise extends in a horizontal plane from the inner wall of the guide plate with one of the two sides adjacent to the right angle fixed to said inner wall in a vertical direction and the other side disposed at the top. To the back side (FIG. 5) of the key guide member 19 are fixed a pair of holders 33 of the same form and material as the first mentioned holders 31 in symmetrical relationship with respect to an imaginary central line dividing said back side into the right and left portions. These holders 33 extend toward the outside of the guide member 19 slantwise with respect to the lengthwise direction thereof in a manner to be set apart from each other, with one of the two sides adjacent to the right angle fixed to the back side 32 in a vertical direction and the other side placed at the top, as is the case with the first mentioned holders 31. The space between a plane defined by the undersides of the flanged portions 24 and a plane defined by the top sides of the triangular holders 31 and 33 is made equal to or slightly larger than the thickness of the printed circuit board 11.

The 18 aperture portions 14 of the printed circuit board 11 are each formed of three sections: (1) an opening 34 for receiving the aforementioned rectangular parallelepiped having substantially the same lengthwise and crosswise measurements as said parallelepiped 20; (2) slots for receiving the guide plates having a length equal or longer than those portions of the guide plates which project from the rectangular parallelepiped 20 and a sufficiently larger width than the thickness of the guide plates to allow the holders 31 to be urged nearer to the guide plates while passing through said slots 35; and (3) a notch 36 formed in that part of the opening 34 which faces the slots 35 and having a sufficient width to allow the holder 33 to be elastically urged more apart from the back side of said guide member while passing through said notch 36 and a sufficient depth to prevent the holders 33 from 1 striking against the bottom wall of said notch 36. The apertures 14 of the printed circuit board 11 are so formed that those adjacent to each other in a horizontal row are arranged in opposite directions. In consequence the later described magnetic reed switches attached to said apertures are disposed ina staggered fashion so as to prevent their permanent magnets from interfering with each other.

There will now be described the sequential steps of fitting the key guide member 19 into the aperture 14 of the printed circuit board 11. When the key guide member 19 is forced into the aperture 14 from above the printed circuit board 11 so as to cause the rectangular parallelepiped 20 to be inserted into the opening 34 and the guide plates 22 and 23 into the slots 35, then the hypotenuses of the holders 33 in the form of a rectangular triangle disposed on the back side 32-of the key guide member 19 abut on the upper edges of the right and left sides of the notch 36 of the aperture 14, as illustrated in FIG. 10. And the hypotenuses of the holders 31 fitted to the guide plates 22 and 23 contact the upper edges of the inner walls of the slots 35. When the key guide member 19 is forced further inward, the elastic holders 31 are gradually thrown toward the guide plates 22 and 23 by the slots 35 according as said insertion advances and the similarly elastic holders 33 are progressively set apart from the back side 32 by the notch 36. When the key guide member 19 is still further pushed in, the holders 31 and 33 pass through the slots 35 and notch 36, and are brought back to the original inclined positions with respect to the guide plates 22 and 23 and the back side 32 as shown in FIG. 14, so as to pinch the printed circuit board 11 together with the flanged portions 24, As a result, the key guide member 19 ceases to move vertically and is firmly inserted into the printed circuit board 11, thus being prevented from falling off simply by pulling. Further, the opening 34 and the rectangular parallelepiped 20 have substantially the same dimensions, the key guide member is not shaken either lengthwise or crosswise, but is firmly set in place.

Referring to FIG. 11, numeral 37 denotes a ribbon-shaped metal key stem having stepped portion 38 formed at the middle point (FIG. 12), that is, the section below there being made broader than that above. Both edges of the lower section are inserted into the grooves 27 so as to cause said key stem 37 to be guided through the elongated hole 26 slidably along the grooves 27. The upper end of the key stem 37 is forcefully inserted into the fitting hole 39 of a push button 40. Between the upper surface of the key guide member 19 and the underside of the push button 40 is disposed a compression coil spring 41 so as to enclose the key stem 37. Normally said spring 41 up wardly urges the push botton 40 and key stem 37, which jointly constitutes the key 12.

Referring to FIG. 14, numeral 42 represents a permanent magnet assuming the form of a rectangular parallelepiped. In that part of one side of the magnet 42 where the magnetic forces acting from both poles are balanced, there is formed a groove 43 intersecting the line of magnetic force substantially at right angles. Said magnet 42 is firmly set in place by applying, for example, an adhesive to that lower portion of the key stem 37 inserted into the key guide member 19 which can be brought into view through the recess 21 formed in the aforementioned rectangular parallelepiped 20, a component of the key guide member 19. The groove 43 is horizontally disposed so as to be exposed to the outside, as shown in FIGS. 11 and 12, and further to be aligned with those parts of the receptacles 28 and 29 into which the magnetic reed switch is fitted. On the upper surface of the permanent magnet 42 is pasted an elastic pad or shock absorber 44 made of elastic material. for example, rubber and having several ribs 45 formed thereon. When the push button 40 is not depressed, said shock absorber 44 abuts on the underside of the shoulder 25, namely, the upper surface of the recess 21.

Referring to FIG. 13, numeral 46 denotes a magnetically operated reed switch, which consists of a pair of switch elements or reed contacts 47 and 48 made of conductive magnetic material and so disposed as to spatially overlap each other at the facing ends and a glass capsule 49 in which they are to be sealed. From the reed contacts 47 and 48 are drawn out lead wires 50 and 51 respectively. The magnetic reed switch 46 is placed between the guide plates 22 and 23 in the undermentioned manner. The lead wire 50 is first inserted into the receptacle 28 and the capsule 49 is properly located by causing that end of the capsule 49 to which the lead wire 50 is fitted to abut on the opening of the receptacle 28 facing the inner wall of the guide plate 22. Thereafter the other end of the capsule 49 is forcefully inserted into the receptacle 29 from below. In this case, it is preferred that the lower end portion 29a (FIG. 11) of the receptacle 29 be formed narrow and that part thereof which holds said other end of the capsule 49 be made just a little narrower than the diameter of said other end of the capsule 49. Thus, when said other end of the capsule 49 is going to be forcefully inserted into the receptacle 29, the notch 30 formed at the top of the receptacle 29 causes it readily to expand due to its elasticity and, when said capsule end passes through the lower end portion 29a, to be contracted again, thereby securely holding said capsule end to prevent it from easily coming off. Thereafter the other ends of the lead wires 50 and 51 are inserted into the corresponding small holes 18 and soldered to the key input circuits 17. That section of a calculator which consists of the key guide member 19, key 12, permanent magnet 42 and magnetic reed switch 46 is hereinafter referred to as a key switch unit." The keyboard switch assembly of FIGS. 1 and 2 is set up by incorporating a required number of key switch units arranged as described above in the printed circuit board 11 and connecting the lead wires 50 and 51 of the magnetic reed switches 46 to the corresponding key input circuits 17 through the small holes 18.

There will now be described the operation of the keyboard switch assembly.

When the key 12 is not depressed as shown in FIG. 13, the depression 43 formed in the permanent magnet 42 fixed to the key stem 37 is brought opposed to the reed contacts 47 and 48, causing said contacts 47 and 48 to be positioned at a point where the magnetic forces acting from the opposite poles are in equilibrium. Accordingly, these contacts 47 and 48 are not magnetized, but remain separated from each other. When the push button 40 is fully depressed, the permanent magnet 42 and key stem 37 are brought downward, causing the groove 43 formed in said magnet 42 to fall to the same extent. As a result, the reed contacts receive different magnetic forces from both poles of magnetic reed switch 46, and contact each other due to magnetization. Accordingly, the key input circuits through the magnetic reed switch 46 are closed to supply required signals to a calculating mechanism (not shown). When released from depression, the key 12 is brought back to its original position by the spring 41, and the groove 43 formed in the permanent magnet 42 is returned to a point facing the contacts of the magnetic reed switch 46. Since the contacts are placed again at the point where the magnetic forces acting from both poles of the permanent magnet 42 are in equilibrium, they are demagnetized to be set apart, cutting off the corresponding key input circuits 17. When the key 12 is brought back to its original position, the ribs 45 of the shock absorber 44 are elastically deformed by abutting on the under side of the shoulder 25, so that the key stem 37 or permanent magnet 42 is prevented from impinging on the shoulder 25 or the underside of the printed circuit board 11. With the keyboard switch assembly of this invention, the keyboard is, as seen from the foregoing description, of the same material as the printed circuit board, thus enabling the key frame of, for example, an electronic calculator to be formed of a single board. Once set up, the present keyboard switch assembly does not require any additional wiring, thus permitting a simple arrangement and offering the advantage of reducing manufacturing cost and facilitating maintenance and inspection. Since the key guide members 19 and printed circuit board are separate components, they can be respectively used with other types of calculator. This invention has further advantages that the key guide members 19 provided with the flanges 24 and holders 31 and 33 can be fitted into the apertures 14 of the printed circuit board 11 without much work; the receptacles 28 and 29 formed in the lower parts of the guide plates 22 and 23 respectively permit the accurate location of the magnetic reed switches 46 and in consequence enable them to be actuated exactly in response to the depression of the keys 12; and the keys 12 each fitted with the shock absorber 44 are relieved of impacts which might otherwise arise at their return to the original positions, thus preventing the failure of a calculator as a whole.

What we claim is: l. A key switch unit comprising a key guide member of synthetic resinous material having flange portions closely contacting the top surface of a flat board, a pendent body extending downwardly therefrom, an elongated hole formed through said flange portions and body, and a switch holding portion provided on said body; means for securing said key guide member to said board; a key havmg a stem longitudinally slidable in said elongated hole, a push button affixed to the upper end of said stem, and a magnet affixed to the lower portion of said stern; and a magnetically operated switch held at said switch holding portion to be actuated by said magnet in response to movement of said stem. 2. The unit according to claim 1 wherein said magnetically operated switch comprises a glass capsule enclosing reed contacts of conductive magnetic material and lead wires for connecting said reed contacts to external circuits, and said switch holding portion comprises a pair of receptacles to hold said glass capsule and lead wires disposed therebetween for arranging said switch at a predetermined position so that said reed contacts open and close in response to movement of said magnet of said key. 3. A key switch unit comprising a key guide member of synthetic resinous material having flange portions closely contacting the top surface of a flat board, a pendent body extending downwardly therefrom, an elongated hole formed through said flange portions and body, and a pair of elastic projections formed on a vertical side wall of said body and disposed below said flange portion at a space equal to the thickness of said board,

hole, and a push button affixed to the upper end of said stem, and a switch arranged to be actuated in response to movement of said stem caused by the operation of said push button. 4. The unit according to claim 3 wherein said elastic projection is a wedge-shaped tab in normal condition and easily inserted into said aperture together with said body in folded condition, and the horizontal upper side thereof closely contacts the undersurface of said board when said body is fully inserted into said aperture.

5. The unit according to claim 3 wherein said key guide member further has a switch holding portion provided on said body, said key further has a magnet affixed to the lower portion of said stem, and said switch is held at said switch holding portion and arranged to be actuated by said magnet in response to movement of said stem.

6. The unit according to claim 5 wherein said switch comprises a glass capsule enclosing reed contacts of conductive magnetic material and lead wires for connecting said reed contacts to external circuits, and said switch holding portion comprises a pair of receptacles to hold said glass capsule and lead wires disposed therebetween for arranging said switch at a predetermined position so that said reed contacts open and close in response to movement of said magnet on said stem.

7. A key switch unit comprising a key guide member perforated with an elongated hole and inserted into an aperture in a flat board and secured to said board;

a key having a stem longitudinally slidable in said elongated hole, a push button affixed to the upperend of said stem, and a magnet affixed to the lower portion of said stem;

spring means for holding said key at an upper rest position;

an elastic pad fitted to the upper surface of said magnet so that said upper surface thereof does not directly strike said board when said key returns to said rest position; and

a magnetically operated switch arranged to be actuated in response to movement of said key caused by the operation of said push button.

8. A keyboard switch assembly comprising a printed circuit board having a plurality of apertures and printed key input circuits;

a plurality of key guide members, each inserted into the aperture and secured to said board;

a plurality of'keys, each having a stem longitudinally slidable in said key guide member and a push button affixed to the upper end of said stem; and

a plurality of switches, each arranged to be actuated in response to movement of said stem caused by the operation of the corresponding push button and connected to the printed key input circuits.

9. The assembly according to claim 8 wherein said key guide member of synthetic resinous material has a switch holding portion and an elongated hole, said stem further has a magnet disposed below said push button, and said switch comprises magnetically operated switch elements and lead wires for connecting said elements to said printed key input circuits, said switch elements being held at said switch holding portion to be actuated by said magnet in response to movement of said stem. 

1. A key switch unit comprising a key guide member of synthetic resinous material having flange portions closely contacting the top surface of a flat board, a pendent body extending downwardly therefrom, an elongated hole formed through said flange portions and body, and a switch holding portion provided on said body; means for securing said key guide member to said board; a key having a stem longitudinally slidable in said elongated hole, a push button affixed to the upper end of said stem, and a magnet affixed to the lower portion of said stem; and a magnetically operated switch held at said swiTch holding portion to be actuated by said magnet in response to movement of said stem.
 2. The unit according to claim 1 wherein said magnetically operated switch comprises a glass capsule enclosing reed contacts of conductive magnetic material and lead wires for connecting said reed contacts to external circuits, and said switch holding portion comprises a pair of receptacles to hold said glass capsule and lead wires disposed therebetween for arranging said switch at a predetermined position so that said reed contacts open and close in response to movement of said magnet of said key.
 3. A key switch unit comprising a key guide member of synthetic resinous material having flange portions closely contacting the top surface of a flat board, a pendent body extending downwardly therefrom, an elongated hole formed through said flange portions and body, and a pair of elastic projections formed on a vertical side wall of said body and disposed below said flange portion at a space equal to the thickness of said board, said key guide member being secured to said board so as to insert the board between said flange portions and said projections when said body is fully inserted into an aperture in said board against the elasticity of said projections; a key having a stem longitudinally slidable in said elongated hole, and a push button affixed to the upper end of said stem, and a switch arranged to be actuated in response to movement of said stem caused by the operation of said push button.
 4. The unit according to claim 3 wherein said elastic projection is a wedge-shaped tab in normal condition and easily inserted into said aperture together with said body in folded condition, and the horizontal upper side thereof closely contacts the undersurface of said board when said body is fully inserted into said aperture.
 5. The unit according to claim 3 wherein said key guide member further has a switch holding portion provided on said body, said key further has a magnet affixed to the lower portion of said stem, and said switch is held at said switch holding portion and arranged to be actuated by said magnet in response to movement of said stem.
 6. The unit according to claim 5 wherein said switch comprises a glass capsule enclosing reed contacts of conductive magnetic material and lead wires for connecting said reed contacts to external circuits, and said switch holding portion comprises a pair of receptacles to hold said glass capsule and lead wires disposed therebetween for arranging said switch at a predetermined position so that said reed contacts open and close in response to movement of said magnet on said stem.
 7. A key switch unit comprising a key guide member perforated with an elongated hole and inserted into an aperture in a flat board and secured to said board; a key having a stem longitudinally slidable in said elongated hole, a push button affixed to the upper end of said stem, and a magnet affixed to the lower portion of said stem; spring means for holding said key at an upper rest position; an elastic pad fitted to the upper surface of said magnet so that said upper surface thereof does not directly strike said board when said key returns to said rest position; and a magnetically operated switch arranged to be actuated in response to movement of said key caused by the operation of said push button.
 8. A keyboard switch assembly comprising a printed circuit board having a plurality of apertures and printed key input circuits; a plurality of key guide members, each inserted into the aperture and secured to said board; a plurality of keys, each having a stem longitudinally slidable in said key guide member and a push button affixed to the upper end of said stem; and a plurality of switches, each arranged to be actuated in response to movement of said stem caused by the operation of the corresponding push button and connected to the printed key input circuits.
 9. The assembly according to claim 8 wherein said key guide member of synthetic resinous material has a switch holding portion and an elongated hole, said stem further has a magnet disposed below said push button, and said switch comprises magnetically operated switch elements and lead wires for connecting said elements to said printed key input circuits, said switch elements being held at said switch holding portion to be actuated by said magnet in response to movement of said stem. 